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Development of Evaluation Methodology for Rolling Shear Properties in Cross Laminated Timber (CLT)

https://research.thinkwood.com/en/permalink/catalogue137
Year of Publication
2013
Topic
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Application
Beams
Author
Zhou, Qinyi
Organization
University of New Brunswick
Year of Publication
2013
Format
Thesis
Material
CLT (Cross-Laminated Timber)
Application
Beams
Topic
Mechanical Properties
Keywords
Span-to-Depth
Rolling Shear Modulus
Two-plate shear test
Load Carrying Capacity
Research Status
Complete
Summary
The rolling shear modulus is very low, leading to rolling shear failure in the cross layer of cross-laminated timber (CLT). The overall objective of this thesis work was to develop an appropriate methodology for measuring the rolling shear properties of CL T. This research consists of three article format chapters, which were aimed at: 1) obtaining a better understanding of advantages and disadvantages of using the bending test and twoplate shear test for determining the rolling shear properties of 3-layer CLT, 2) investigating the influence of growth ring orientation and laminates thickness of cross layer on the rolling shear properties, and 3) verifying the feasibility of two-plate shear test method for measuring the rolling shear properties of 3-layer CL T beam. It is recommended that the two-plate shear test be used as a testing method for measuring the rolling shear modulus of a cross layer, which can be used to calculate the deflection of a 3-layer CLT beam using the shear analogy method at a given span-to-depth ratio ranging from 6 to 50. An adjustment factor (a) was proposed to predict the deflection under the centre-point bending test at various span-to-depth ratios. The two-plate shear test method can also be used to measure the rolling shear strength, and can provide a reasonable estimate of the load-carrying capacity of 3-layer CLT beam at a relatively large span-to-depth ratio, but a conservative estimate at a small span-to-depth ratio. In summary, it shall be feasible to adopt the two-plate shear test for determining the rolling shear modulus and strength of cross layer in CLT.
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Effect of Growth Ring Orientation on the Rolling Shear Properties of Wooden Cross Layer Under Two-Plate Shear Test

https://research.thinkwood.com/en/permalink/catalogue635
Year of Publication
2014
Topic
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Author
Zhou, Qinyi
Gong, Meng
Chui, Ying Hei
Mohammad, Mohammad
Year of Publication
2014
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Topic
Mechanical Properties
Keywords
Growth Ring Orientation
Rolling Shear Modulus
Rolling Shear Strength
Spruce
Two-plate shear test
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 10-14, 2014, Quebec City, Canada
Summary
The design and application of cross laminated timber (CLT) is s trongly influenced by rolling shear properties of cross layers. Hence, predicting the mechanical behaviour of CLT requires accurate information about its rolling shear properties. In this study, black spruce wood laminates with three different growth ring orientations (flat sawn, in-between, quarter sawn) were edge glued to produce wooden cross layer (WCL). Two-plate shear tests were carried out on WCL to investigate the influence of growth ring orientation on the rolling shear properties. The experimental results showed that the growth ring orientation had a significant effect on rolling shear modulus of WCL, however, almost no effect on the rolling shear strength. The WCL of in-between end grain had the maximum rolling shear modulus of 89MPa and rolling sh ear strength of 2.13 MPa.
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Hybrid Beech and Spruce Cross-Laminated Timber

https://research.thinkwood.com/en/permalink/catalogue1547
Year of Publication
2016
Topic
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Author
Aicher, Simon
Hirsch, Maren
Christian, Zachary
Year of Publication
2016
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Topic
Mechanical Properties
Keywords
Beech
Rolling Shear Modulus
Rolling Shear Strength
Shear Tests
Compression Shear
Bending Tests
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 1147-1155
Summary
The presented work examines the rolling shear properties of beech wood for the novel application as cross-layers in hybrid cross-laminated timber. Rolling shear modulus and strength of beech were determined by three different approaches: i) two-plate shear tests on single beech board slabs, and ii) compression shear and iii) bending tests on hybrid CLT specimens based on the test methods defined in EN 16351. The CLT specimens were cut from two industrially manufactured hybrid three-layered CLT-plates with a beech cross-layer and spruce outer layers. The rolling shear modulus results obtained from the single board tests and the bending tests agreed well and were within the range of 350 - 370 N/mm². The characteristic rolling shear strength obtained from the bending tests was determined as 2.6 N/mm², where the failure was often governed by longitudinal shearing of the spruce laminations. Hybrid CLT-plates demonstrate a highly improved strength and deflection behaviour versus homogenous spruce CLT-plates and result in not only a mechanically superior product but also allow for a greatly simplified design approach.
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Measurement of Rolling Shear Modulus of Cross Laminated Timber: Exploratory Study Using Downscaled Specimens Under Variable Span Bending Tests

https://research.thinkwood.com/en/permalink/catalogue605
Year of Publication
2012
Topic
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Author
Zhou, Qinyi
Gong, Meng
Chui, Ying Hei
Mohammand, Mohammand
Publisher
IEEE
Year of Publication
2012
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Topic
Mechanical Properties
Keywords
Rolling Shear Modulus
Three Point Bending Test
Steel
Span-to-Depth Ratio
Growth Ring Orientation
Conference
International Conference on Biobase Material Science and Engineering
Research Status
Complete
Notes
October 21-23, 2012, Changsha, China
Summary
The purpose of this study was to measure the rolling shear modulus of Cross Laminated Timber (CLT), which was achieved by conducting 3-point bending tests with variable span using downscaled sandwich specimens. Two types of sandwich specimens were employed: steel-wood-steel (SWS) and wood-wood-wood (WWW). Experimental results from SWS specimens were verified with those predicted from WWW ones through the shear analogy method. Effects of span-to-depth ratio (l/h) and growth ring orientation on rolling shear modulus (G RT ) were also examined. It was found that the average deflection of WWW specimens tested at l/h of 6.5 could be well predicted using the shear analogy method based on true elasticity of modulus (E m ) and G RT of the cross layer measured using SWS specimens under variable span tests. The results also showed that the cross layer of `in-between' growth ring orientation could gain the higher rolling shear modulus than that of flat sawn or quarter sawn one.
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Planar Shear and Bending Properties of Hybrid CLT Fabricated with Lumber and LVL

https://research.thinkwood.com/en/permalink/catalogue1324
Year of Publication
2017
Topic
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
LVL (Laminated Veneer Lumber)
Author
Wang, Zhiqiang
Fu, Hongmei
Gong, Meng
Luo, Jiayan
Dong, Weiqun
Wang, Ting
Chui, Ying Hei
Publisher
ScienceDirect
Year of Publication
2017
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
LVL (Laminated Veneer Lumber)
Topic
Mechanical Properties
Keywords
Rolling Shear Modulus
Rolling Shear Strength
SPF
Failure Modes
Research Status
Complete
Series
Construction and Building Materials
Summary
Planar (rolling) shear properties in cross laminated timber (CLT) is an important factor that should be considered for CLT structural components with short span or openings. The planar shear properties of SPF (Spruce-pine-fir) dimension lumber and laminated veneer lumber (LVL) were measured using a modified approach in this study. The failure modes in planar shear tests were investigated by visual inspection and optical microscope. Hybrid CLT (HCLT) was fabricated using lumber and/or LVL, and its bending properties (in major strength direction) were evaluated. It was found that SPF had higher planar shear strength and modulus than LVL. The failure mode of HCLT with LVL as cross layer in planar shear test was shear failure along the glue line direction, however, the typical failure modes of HCLT with SPF as cross layer in planar shear test included rolling shear failure along the growth ring direction, shear failure along the wood ray direction and shear failure along glue line direction. The bending properties of the generic CLT had been improved by using LVL as parallel layers and been reduced by using LVL as cross layer. The planar shear failure of cross layer in the zone between loading point and support point was the typical failure mode of CLT and HCLT in bending test.
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